Prognostic factors for extracorporeal shock‐wave lithotripsy of ureteric stones
A multivariate analysis study

Abstract

Objective: To define factors that have a significant impact on the stone‐free rate after extracorporeal shock‐wave lithotripsy (ESWL) of ureteric stones using multivariate analysis.

Material and Methods: Between February 1992 and February 2002, a total of 938 patients with ureteric stones were treated with in situ ESWL using the Dornier MFL 5000 lithotripter. The outcome of treatment was evaluated after 3 months and failure was defined as the presence of any residual stones. The stone‐free rate was correlated with patient characteristics (age, sex and radiological renal picture) and stone features (site, side, length, width, nature, opacity and the presence of ureteral stents). Factors with a significant impact on the stone‐free rate using the χ ² test were further analyzed using multivariate analysis.

Results: Overall, the stone‐free rate was 88.7%. Repeat treatment was required in 50.4% of cases. Post‐ESWL complications were observed in 32 cases (3.4%), including static steinstrasse in 19 (2%). Auxiliary procedures were needed in 28 cases (3%). Using the χ ² test, only three factors had a significant impact on the stone‐free rate, namely stone site, the transverse diameter of the stone and the presence of a ureteral stent. The stone‐free rate was highest for stones located in the lumbar ureter (436/470; 92.8%) and lowest for those located in the pelvic ureter (268/324; 82.7%) (p = 0.0017). Stones with a transverse diameter of ≤1 cm were associated with a stone‐free rate of 89.7% (715/797), compared to 83% (114/141) for those with a transverse diameter of >1 cm (p = 0.017). Non‐stented patients had a stone‐free rate of 89.8% (732/815), compared to 81.3% (100/123) for stented patients (p = 0.006). On multivariate analysis, these three factors maintained their statistical significance. A logistic regression model was designed to estimate the probability of stone‐free status after ESWL.

Conclusion: The site and transverse diameter of the stone and the presence of a ureteral stent are the only significant predictors of success of ESWL therapy for ureteric stones.

• extracorporeal shock‐wave lithotripsy
• prognostic factors
• ureteric calculi